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Chlorotrifluorosilane is an inorganic gaseous compound with formula SiClF3 composed of silicon, fluorine and chlorine. It is a silane that substitutes hydrogen with fluorine and chlorine atoms.

Production

By heating a mixture of anhydrous aluminium chloride and sodium hexafluorosilicate to between 190 and 250 °C a mixture of gases containing chlorotrifluorosilane is given off. These are condensed at -196 °C degrees and fractionally distilled at temperatures up to -78 °C.[2]

SiClF3 can be made by reacting silicon tetrachloride and silicon tetrafluoride gases at 600 °C, producing a mixture of fluorochlorosilanes including about one quarter SiClF3.[3]

SiClF3 can be made by reacting silicon tetrachloride with antimony trifluoride. An antimony pentachloride catalyst assists. The products are distilled to separate it out from tetrafluorosilane and dichlorodifluorosilane.[4][5][6]

At high temperatures above 500 °C silicon tetrafluoride can react with phosphorus trichloride to yield some SiClF3. This is unusual because SiF4 is very stable.[7]

Silicon tetrachloride can react with trifluoro(trichloromethyl)silane to yield SiClF3 and CCl3SiCl3.[8]

2-Chloroethyltrifluorosilane or 1,2-dichloroethyltrifluorosilane can be disassociated by an infrared laser to yield SiClF3 and C2H4 (ethylene) or vinyl chloride. By tuning the laser to a vibration frequency of a particular isotope of silicon, different isotopomers can be selectively broken up in order to have a product that only concentrates one isotope of silicon. So silicon-30 can be increased to 80% by using the 934.5 cm−1 line in a CO2 laser.[9]

The first published preparation of SiClF3 by Schumb and Gamble was by exploding hexafluorodisilane in chlorine: Si2F6 + Cl2 → 2SiClF3. Other products of this explosion may include amorphous silicon, SiCl2F2 and SiF4.[10]

Chlorine reacts with silicon tetrafluoride in the presence of aluminium chips at 500-600 °C to make mostly silicon tetra chloride and some SiClF3.[11]

Mercuric chloride when heated with SiF3Co(CO)4 breaks the bond to form a 90% yield of SiClF3.[12]

The combination of SiF4 and chlorodimethylphosphine yields some SiClF3.[13]

Trifluorosilane SiHF3 reacts with gaseous chlorine to yield SiClF3 and HCl.[14]

Properties

Molecular size and angles

Bond length for Si–Cl is 1.996 Å and for Si–F is 1.558 Å. The bond angle ∠FSiCl = 110.2° and ∠FSiF = 108.7°.[4] The bond length between silicon and chlorine is unusually short, indicating a 31% double bond. This can be explained by the more ionic fluoride bonds withdrawing some charge allowing a partial positive charge on the chlorine.[15]

The molecular dipole moment is 0.636 Debye.[4]

Bulk properties

Between 129.18 and 308.83 K the vapour pressure in mm Hg at temperature T in K is given by log10 P = 102.6712 -2541.6/T -43.347 log10 T + 0.071921T -0.000045231 T2.[16]

The heat of formation of chlorotrifluorosilane is -315.0 kcal/mol at 298K.[17]

Reactions

Chlorotrifluorosilane is hydrolysed by water to produce silica.

Chlorotrifluorosilane reacts with trimethylstannane ((CH3)3SnH) at room temperature to make trifluorosilane in about 60 hours.[18]

Use

Proposed uses include a dielectric gas with a high breakdown voltage, and low global warming potential, a precursor for making fluorinated silica soot, and a vapour deposition gas.

Related substances

Chlorotrifluorosilane can form an addition compound with pyridine with formula SiClF3.2py (py=pyridine)[19] An addition compound with trimethylamine exists.[20][21] This addition compound is made by mixing trimethylamine vapour with Chlorotrifluorosilane and condensing out a solid at -78 °C. If this was allowed to soak in trimethylamine liquid for over eight hours, a diamine complex formed (2Me3N·SiClF3).[21] At 0° the disassociation pressure of the monoamine complex was 23 mm Hg.[21]

SiClF3− is a trigonal bipyramidal shape with a Cl and F atom on the axis. It is formed when gamma rays hit the neutral molecule.[22]

Chlorotetrafluorosilicate (IV) (SiClF4−) can form a stable a pale yellow crystalline compound tetraethylammonium chlorotetrafluorosilicate.[23]

References

  1. ^ Inorganic Syntheses, Inc (22 September 2009). Inorganic Syntheses. John Wiley & Sons. p. 266. ISBN 9780470132654. {{cite book}}: |first1= has generic name (help)
  2. ^ Schmeißer und Herber t Jenkne r, Martin; Jenkner, Herbert (1952). "Zurr Kenntnis anorganischer Säurefluoride (i) Über Reaktione n des Siliciumtetrafluorids (bzw. des Natriumsilicofluorids )" (PDF). Verlag Zeitschrift für Naturforschung: 191–192. doi:10.1515/znb-1952-0310. S2CID 95929863.
  3. ^ US 2395826, Hill, Julian W. & Lindsey Jr. V, Richard, "Preparation of chlorofluorosilanes", issued 3 May 1946 
  4. ^ a b c Cox, A.P.; Gayton, T.R.; Rego, C.A. (November 1988). "Microwave spectrum, structure, quadrupole coupling constant and dipole moment of chlorotrifluorosilane and iodotrifluorosilane". Journal of Molecular Structure. 190: 419–434. Bibcode:1988JMoSt.190..419C. doi:10.1016/0022-2860(88)80301-6.
  5. ^ Booth, Harold Simmons; Swinehart, Carl F. (July 1935). "The Fluorochlorosilanes". Journal of the American Chemical Society. 57 (7): 1333–1337. doi:10.1021/ja01310a050.
  6. ^ Annual Reports on the Progress of Chemistry. 1940. p. 151.
  7. ^ Suresh, B.S.; Padma, D.K. (September 1985). "Halogen exchange reactions of silicon tetrafluoride with phosphorus trichloride and phosphoryl chloride". Journal of Fluorine Chemistry. 29 (4): 463–466. Bibcode:1985JFluC..29..463S. doi:10.1016/S0022-1139(00)85111-8.
  8. ^ Weidenbruch, Manfred; Pierrard, Claude (April 1977). "Reaktionen von Halogeniden des Siliciums, Germaniums und Zinns mit Diazomethan und Dichlorcarben- Transfer-Agentien". Chemische Berichte (in German). 110 (4): 1545–1554. doi:10.1002/cber.19771100437.
  9. ^ Dementyev, Petr S.; Nizovtsev, Anton S.; Chesnokov, Evgenii N. (July 2011). "Infrared photoreaction of 2-chloroethyltrifluorosilane". Journal of Photochemistry and Photobiology A: Chemistry. 222 (1): 77–80. Bibcode:2011JPPA..222...77D. doi:10.1016/j.jphotochem.2011.05.004.
  10. ^ Schumb, Walter C.; Gamble, E. Lee (October 1932). "Fluorochlorides of Silicon". Journal of the American Chemical Society. 54 (10): 3943–3949. doi:10.1021/ja01349a018.
  11. ^ Zuckerman, J. J (17 September 2009). Inorganic Reactions and Methods, the Formation of Bonds to Halogens. John Wiley & Sons. p. 361. ISBN 9780470145388.
  12. ^ Zhou, Yong (3 September 2013). Organosilicon Chemistry: 2: Plenary Lectures Presented at the Second International Symposium on Organosilicon Chemistry. Elsevier. p. 443. ISBN 9781483284828.
  13. ^ Journal of the Chinese Chemical Society. Chinese Chemical Society. 1999. p. 450. ISBN 9780021926541.
  14. ^ Gmelin, Leopold (1996). Silicon: Supplement volume. p. 103. ISBN 9783540937289.
  15. ^ Pauling, Linus (January 1960). The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry. Cornell University Press. p. 312. ISBN 0801403332.
  16. ^ Yaws, Carl L.; Nijhawan, Sachin; Bu, Li (1995). "Appendix C Coefficients for vapor pressure equation". Handbook of Vapor Pressure. Vol. 4. pp. 352–357. doi:10.1016/S1874-8813(06)80008-9. ISBN 9780884153948.
  17. ^ Gordon, M. S.; Francisco, J. S.; Schlegel, H. B. (1993). "THEORETICAL INVESTIGATIONS OF THE THERMOCHEMISTRY AND THERMAL DECOMPOSITION OF SILANES, HALOSILANES, AND ALKYLSILANES" (PDF). Advances in Silicon Chemistry. 2. JAI Press: 153.
  18. ^ Gmelin, Leopold (1996). Silicon: Supplement volume. Springer. p. 83. ISBN 9783540937289.
  19. ^ Hensen, Karl; Wagner, Hans Bernhard (February 1976). "Über einige Verbindungen gemischter Siliciumhalogenide mit Pyridin". Chemische Berichte (in German). 109 (2): 411–414. doi:10.1002/cber.19761090201.
  20. ^ Sommer, Leo Harry (1965). Stereochemistry, mechanism and silicon: An introduction to the dynamic stereochemistry and reaction mechanisms of silicon centers. McGraw-Hill. pp. 19–20.
  21. ^ a b c Fergusson, J. E.; Grant, D. K.; Hickford, R. H.; Wilkins, C. J. (1959). "21. Co-ordination of trimethylamine by halides of silicon, germanium, and tin". Journal of the Chemical Society (Resumed): 99–103. doi:10.1039/JR9590000099.
  22. ^ Hasegawa, Akinori; Uchimura, Schunichiro; Koseki, Kohji; Hayashi, Michiro (January 1978). "ESR spectrum and structure of the SiF3Cl− radical anion". Chemical Physics Letters. 53 (2): 337–340. Bibcode:1978CPL....53..337H. doi:10.1016/0009-2614(78)85410-4.
  23. ^ Edwards, H.G.M.; Fawcett, V.; Rose, S.J.; Smith, D.N. (May 1992). "The preparation and Raman spectroscopic study of the chlorotetrafluorosilicate (IV) ion, SiF4Cl−". Journal of Molecular Structure. 268 (4): 353–361. Bibcode:1992JMoSt.268..353E. doi:10.1016/0022-2860(92)80222-4.

Extra reading

  • Wodarczyk, F.J; Wilson, E.B (March 1971). "Radio frequency-microwave double resonance as a tool in the analysis of microwave spectra". Journal of Molecular Spectroscopy. 37 (3): 445–463. Bibcode:1971JMoSp..37..445W. doi:10.1016/0022-2852(71)90176-7.
  • Sheridan, John; Gordy, Walter (March 1950). "Microwave Spectra and Molecular Constants of Trifluorosilane Derivatives. SiF3H, SiF3CH3, SiF3Cl, and SiF3Br". Physical Review. 77 (5): 719. Bibcode:1950PhRv...77..719S. doi:10.1103/PhysRev.77.719.
  • Sheridan, John; Gordy, Walter (1951). "The Microwave Spectra and Molecular Structures of Trifluorosilane Derivatives". The Journal of Chemical Physics. 19 (7): 965. Bibcode:1951JChPh..19..965S. doi:10.1063/1.1748418.
  • Ault, Bruce S. (December 1979). "Infrared matrix isolation studies of the M+SiF5- ion pair and its chlorine-fluorine analogs". Inorganic Chemistry. 18 (12): 3339–3343. doi:10.1021/ic50202a012.
  • Stanton, C. T.; McKenzie, S. M.; Sardella, D. J.; Levy, R. G.; Davidovits, Paul (August 1988). "Boron atom reactions with silicon and germanium tetrahalides". The Journal of Physical Chemistry. 92 (16): 4658–4662. doi:10.1021/j100327a020.
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